Closure for crucibles used for aluminothermic reactions

ABSTRACT

This invention relates to an improvement in a closure for crucibles used for aluminothermic reactions comprising a tap pin, a sealing material, and refractory sand, the improvement comprising a sealing material of inorganic fibers covering the tap pin.

United States Patent [191 Guntermann Aug. 27, 1974 CLOSURE FOR CRUCIBLESUSED FOR [56] References Cited ALUMINOTHERMIC REACTIONS UNITED STATESPATENTS [75] Inventor: Hans Guntermann, Essen-Steele, 2,024,132 12/1935Sander 75 /27 Germany OTHER PUBLICATIONS [73] Asslgnee: E P GmbH EssenPublication: Thermit Mill and Foundry Practice; pages Steele, Germany[22] Filed: May 21, 1973 Primary Examiner-Gerald A. Dost [21] Appl'362310 Attorney, Agent, or Firm]ames E. Bryan [30] Foreign ApplicationPriority Data [57] ABSTRACT June 22, 1972 Germany 2230430 This inventionrelates to an improvement in a closure for crucibles used foraluminothermic reactions com- [52] US. Cl 266/34 R, 266/38, 75/27prising a tap pin, a Sealing material, and refractory [51] Int. Cl. C2lc7/00 Sand, the i rovement comprising a sealing material [58] Field ofSearch 266/38, 34 R; 164/53, 54, of inorganic fibers covering the tappin 164/80, 123; 75/23, 27; 222/DIG. l9, DIG. 20

2 Claim, 2 Drawing Figures CLOSURE FOR CRUCIBLES USED FOR ALUMINOTHERMICREACTIONS The present invention relates to a closure for crucibles usedfor aluminothermic reactions, composed of a nail-like tap pin, a sealingcompound, and highly re fractory sand.

Employed for the purpose of carrying out aluminothermic reactions aregenerally conical crucibles composed of a sheet metal jacket, arefractory lining inserted into this jacket, and an exchangeabledischarge nozzle which must be closed anew prior to each filling of thecrucible. Serving as closure means are a nail-like tap pin, a sealingmaterial, and refractory sand, for example corundum sand. The sealingmaterial is asbestos which, when received, is prepared in the form ofsmall plates, and the required number of the small plates, which latterare pulverized or ground to asbestos wool, prior to being used, isdetermined by the size of the cru cible.

In order to obtain, or bring about, the closure, the tap pin issuspended in, or placed into, the opening of the discharge nozzle; thehead of the pin closing the opening of the nozzle is sealed with thepulverized asbestos wool, and the asbestos seal is covered with a layerof refractory sand.

The known crucible closure which has been made in this way for manydecades involves a number of disadvantages which are due to the use ofasbestos wool as a sealing material. It has been found time and again,for example, that portions of the finely pulverized asbestos fibers arepulled or carried along by the discharging aluminothermically producedsteel and remain within the steel where they can give rise to defects.

Another disadvantage which is connected with asbes' tos consists in thatit easily absorbs moisture, particularly when pulverized in moistsurroundings, and moreover very frequently contains carbonaceouscompounds. Both constituents may lead to the formation of gas during thealuminothermic reaction, and therewith to porous welds.

Added thereto more recently was the discovery that dealing with orhandling asbestos which was heretofore indispensable for obtaining thecrucible closure may cause an illness similar to silicosis, which isreferred to as asbestosis.

It is the object of the present invention to provide a sealing materialfor the tap pin which is present in compact form while neverthelessbeing sufficiently flexible to accomplish the sealing effect without apulverization of the material, which furthermore does not affect thealuminothermic reaction, and additionally is not injurious to health.

This object is obtained, in accordance with the present invention, with,or by virtue of, the use of inorganic fibers covering the tap pin. Smallfleece plates, or platelets, made from these fibers have been found tobe particularly advantageous for this purpose.

The invention will now be further described hereinafter on the basis ofthe accompanying drawings, wherein FIG. 1 illustrates a fleece plate 1prepared from inorganic fibers, and

FIG. 2 illustrates the inventive closure means of a crucible used foraluminothermic reactions.

As shown in the drawing, the reaction crucible is composed of arefractory for example magnesite lining 4 which is inserted into a sheetmetal sleeve 2 with an intermediate layer of sand 3. Inserted into thelower part of the crucible is an outlet nozzle 5 which must be closedanew prior to each filling or charge. For purposes of closing, a tap pin6 is suspended into the opening of the discharge nozzle 5; the head ofthe tap pin 6 is covered with the inventive fleece platelet of inorganicfibers, and the fleece platelet 1 is subsequently covered with a layerof refractory sand 7, for example corundum.

It has been found that especially well suited for use in the presentinvention are inorganic fibers composed of approximately 43 to 52percent by weight of Al O 46 to 54 percent by weight of SiO 0.06 to 1.0percent by weight of B 0 and 0.1 to 2.0 percent by weight of one or morealkalies, such as Na O, for example. Such products are obtainable, forinstance, under the trade names of Fiberfrax" or Kaowoolf The productmay be prepared by melting a mixture of, inter alia, aluminum oxide,silicon dioxide, and small amounts of boric acid at about l,650C, andblowing the discharging melt apart by a strong air blast.

Subsequently yielded therefrom in a manner known per se is a fiber whichis further processed for example to wool, mats, molding material, orfleece. It was particularly surprising to find that, when using thissubstance, the amounts of B 0 contained therein are absorbed by the slagand will not impair the mechanical properties of the aluminothermicallyproduced steel, which is relatively sensitive to small boron additions.This phenomenon probably is due to the fact that the small plate offiber fleece becomes coated with a slag layer and floats through themelt in the slag layer where it very frequently can be found again,practically undamaged.

It is equally possible to use small fleece plates of pure Si0 fibers. Ofimportance is the fact that the fleece platelets have adequatemechanical properties, but that a flexibility be retained which willassure a flawless sealing of the tap pin in the reaction crucible. It isparticularly advantageous that the materials to be used according to thepresent invention can no longer adversely affect health, and thatdamaging inclusions in the steel are avoided. The latter was completelyunexpected.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. In a closure for crucibles used for aluminothermic reactionscomprising a tap pin, a sealing material, and refractory sand, theimprovement comprising a sealing material of fibers composed of A1 0 SiOB 0 and alkali.

2. In a closure for crucibles used for aluminothermic reactionscomprising a tap pin, a sealing material, and refractory sand, theimprovement comprising a sealing material of fibers of SiO

2. In a closure for crucibles used for aluminothermic reactionscomprising a tap pin, a sealing material, and refractory sand, theimprovement comprising a sealing material of fibers of SiO2.